The present invention relates to a magnetic thin film exhibiting soft magnetism, a recording head generating a magnetic field to magnetize an external medium, and a magnetic thin film forming method of forming the magnetic thin film.
In recent years, with the spread of computers, a large quantity of information has been daily dealt with, and as a device for recording such a large quantity of information, for example, a hard disk device (HDD: Hard Disk Drive) has been used. The HDD is provided with a magnetic disk as a recording medium a surface of which is made of a magnetic material, and a recording head having a fine coil and further a magnetic pole made of a soft magnetic material, magnetized by the coil, and transmitting a magnetic field generated from the coil, disposed near the above magnetic disk, wherein the surface of the magnetic disk is magnetized by each fine region (1-bit region) by the magnetic field transmitted through the magnetic pole, information is recorded as the direction of magnetization of the fine region.
The recording density of information recorded on a magnetic disk is increasing year by year, and it is known that the magnetic disk on which information is recorded at such an increased recording density must have a high coercive force. On the other hand, a recording head recording information on this magnetic disk must reverse each magnetization of the magnetic disk in which the coercive force has been thus enhanced. For this reason, in order to be able to generate a strong magnetic field, the magnetic pole of the recording head is required to be made of a material superior in soft magnetism (the permeability xcexc is high) and high in saturation magnetic flux density Bs.
Besides, attendant upon such an increase in recording density, a necessity in which the magnetic field is generated at a high recording frequency by the recording head arises. However, in such a high recording frequency, an eddy current arises on the magnetic pole of the recording head and soft magnetic characteristics such as the above permeability xcexc and magnetic flux density B deteriorate. To suppress this deterioration of soft magnetic characteristics, it suffices that the affection by the eddy current on the soft magnetic characteristics is suppressed by raising the electric resistivity xcfx81 of the magnetic pole. Since a permalloy plating film conventionally used as a magnetic pole material of the recording head has a low electric resistivity xcfx81 as about 20 xcexcxcexa9cm, to the recording head used at a recording frequency of 100 MHz of more, a magnetic pole material with a higher electric resistivity xcfx81 is required.
As a film having soft magnetism and having a high electric resistivity xcfx81, for example, an Fexe2x80x94Bxe2x80x94Al xe2x80x94O microcrystalline magnetic film is reported in Patent Application Laid-open No. 9-115729. Besides, in Patent Application Laid-open No. 7-86035 and Patent Application Laid-open No. 7-86036, microcrystalline magnetic films with high electric resistivities xcfx81 in which N is added in Fexe2x80x94Alxe2x80x94O or the like have been proposed.
However, since any of these microcrystalline magnetic films has an organization of a structure in which a ceramics phase such as alumina having a low magnetic moment covers a microcrystalline phase having a high magnetic moment, although the electric resistivity xcfx81 is high, there is a problem that the saturation magnetic flux density Bs and permeability xcexc are low, and so it is inferior in aptitude as a magnetic pole material for recording head.
In view of the above circumstances, the present invention aims to provide magnetic thin films and magnetic thin film forming methods simultaneously having a high saturation magnetic flux density Bs, a high permeability xcexc, and a high electric resistivity xcfx81, and recording heads having a magnetic pole simultaneously having a high saturation magnetic flux density Bs, a high permeability xcexc, and a high electric resistivity xcfx81.
A magnetic thin film of the present invention that achieves the above object is characterized by being a polycrystalline film comprising:
Fe whose content is not less than 57.5 atomic % and not more than 94.5 atomic %;
one or more kinds of elements selected from the element group of Al, B, Ga, Si, Ge, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Rh, whose whole content is not less than 1 atomic % and not more than 15 atomic %;
N whose content is not less than 0.5 atomic % and not more than 10 atomic %; and
O whose content is not less than 1.5 atomic % and not more than 22.5 atomic %.
The polycrystalline film mentioned here means not one having an organization having a structure in which a ceramics phase covers a microcrystalline phase, like the above-described conventional magnetic thin films, but a polycrystalline film made up of crystal particles fundamentally having magnetism though permitting precipitation of substances to grain boundaries.
As will be described in detail in the below embodiment and examples, this magnetic thin film simultaneously has a high saturation magnetic flux density Bs, a high permeability xcexc, and a high electric resistivity xcfx81. It is thinkable that this magnetic thin film has a high saturation magnetic flux density Bs and a high permeability xcexc because this magnetic thin film has a characteristic in composition that the content of Fe is high in comparison with the above-described conventional magnetic thin films, and includes no ceramics phase or even if includes, the quantity of ceramics phase is a little. Besides, it is thinkable that since this magnetic thin film is such a polycrystalline film as described above and crystal particles are that in accordance with the above-described contents, to Fe, one or more kinds of elements selected from the above element group, O, and N are solid-solved, even if not being covered with a ceramics phase, it has a high electric resistivity xcfx81.
As will be described in the below examples, the magnetic thin film of the above present invention is preferable in which the saturation magnetic flux density Bs is not less than 1.6 T and the electric resistivity xcfx81 is not less than 30 xcexcxcexa9cm. Besides, this magnetic thin film is preferable in which the permeability xcexc is not less than 500.
The magnetic thin film of the above present invention is preferably a polycrystalline film made up of crystal particles whose mean particle diameter is not more than 15 nm.
As will be described in the below embodiment and examples, in the magnetic thin film in which the saturation magnetic flux density Bs is not less than 1.6 T, the electric resistivity xcfx81 is not less than 30 xcexcxcexa9cm, and further the permeability xcexc is not less than 500, the mean particle diameter of crystal particles is actually not more than 15 nm. It is thinkable that the characteristic in organization of being made up of crystal particles of such small particle diameter is also effective for improvements of the above saturation magnetic flux density Bs, electric resistivity xcfx81, and permeability xcexc. For example, it is thinkable that by the particle diameter of crystal particles decreasing, the effective magnetic anisotropy Heff decreases, and with this decrease in effective magnetic anisotropy Heff, the permeability xcexc increases.
A recording head of the present invention that achieves the above object is a recording head which has a coil generating a predetermined magnetic field and a soft magnetic member magnetized by the magnetic field generated from the coil and which magnetizes an external medium by the magnetic field generated by the coil and transmitted by the soft magnetic member, characterized in that
the above soft magnetic member is a polycrystalline film comprising:
Fe whose content is not less than 57.5 atomic % and not more than 94.5 atomic %;
one or more kinds of elements selected from the element group of Al, B, Ga, Si, Ge, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Rh, whose whole content is not less than 1 atomic % and not more than 15 atomic %;
N whose content is not less than 0.5 atomic % and not more than 10 atomic %; and
O whose content is not less than 1.5 atomic % and not more than 22.5 atomic %.
Since the soft magnetic member of this recording head is the same as the above-described magnetic thin film of the present invention, this soft magnetic member takes the same operation/effect of the above-described magnetic thin film of the present invention.
Since this soft magnetic member simultaneously has a high saturation magnetic flux density Bs, a high permeability xcexc, and a high electric resistivity xcfx81, the recording head using this soft magnetic member can generate a strong magnetic field at a high recording frequency and record information on a recording medium such as a magnetic disk at a high recording density.
In the recording head of the above present invention, the above soft magnetic member is preferably a polycrystalline film made up of crystal particles whose mean particle diameter is not more than 15 nm.
Since the soft magnetic member of this recording head is the same as the above-described magnetic thin film that is a polycrystalline film made up of crystal particles whose mean particle diameter is not more than 15 nm, this soft magnetic member takes the same operation/effect of this magnetic thin film.
A magnetic thin film forming method of the present invention that achieves the above object is a magnetic thin film forming method that forms a magnetic thin film comprising Fe, one or more kinds of elements selected from the element group of Al, B, Ga, Si, Ge, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Rh, N, and O, on a predetermined substrate by a sputtering process, characterized in that
in order that the content of Fe in the above magnetic thin film may be not less than 57.5 atomic % and not more than 94.5 atomic %, the whole content of one or more kinds of elements selected from the above element group, in the above magnetic thin film, may be not less than 1 atomic % and not more than 15 atomic %, the content of N in the above magnetic thin film may be not less than 0.5 atomic % and not more than 10 atomic %, and further the content of O in the above magnetic thin film may be not less than 1.5 atomic % and not more than 22.5 atomic %,
the magnetic thin film is formed, while controlling the quantities and ratios of materials composing a target, the flow rate and gas mixture ratio of sputter gas, and the electric power applied to the target.
As will be described in detail in the below embodiment and examples, the magnetic thin film formed by this magnetic thin film forming method simultaneously has a high saturation magnetic flux density Bs, a high permeability xcexc and a high electric resistivity xcfx81.
In the magnetic thin film forming method of the above present invention, during the formation of the magnetic thin film on the above substrate and after the film formation, the temperature of the above substrate is preferably maintained at 200xc2x0 C. or less.
The magnetic thin film formed with keeping the temperature of the substrate 200xc2x0 C. or less according to this magnetic thin film forming method has a high electric resistivity xcfx81 and good soft magnetic characteristics and, for example, as will be described later in detail in examples, has a high saturation magnetic flux density Bs.
Besides, in case that the magnetic thin film formed by this magnetic thin film forming method is used as a soft magnetic material for a magnetic pole of a composite-type magnetic head made up of a recording head and a reproducing head, since the substrate temperature upon formation of this magnetic thin film is low as 200xc2x0 C. or less, the reproducing head is kept in a desirable state without detracting the reproduction characteristics.
As described above, according to the present invention, there are provided a magnetic thin film simultaneously having a high saturation magnetic flux density, a high permeability and a high electric resistivity as well as a method of forming the magnetic thin film, and a recording head having a magnetic pole simultaneously possessing a high saturation magnetic flux density, a high permeability, and a high electric resistivity.